ROME — The European Community, fed up with unceasing bloodshed in the Balkans, imposed economic sanctions against Yugoslavia on Friday and called on the United Nations to declare a global oil embargo.

The toughest collective measures ever enacted by a united Europe were targeted principally against Serbia, which the EC has declared the aggressor in its war against the breakaway Yugoslav republic of Croatia.

Ending a two-day summit here, the 16 NATO nations chimed in with a condemnation of their own against the violence in Yugoslavia that worsens daily, despite repeated cease-fires brokered by the EC.

A dozen truces, announced since fighting began in June after Croatia's declaration of independence, have all collapsed immediately. In a counterpoint to the diplomatic initiative by a frustrated Europe, new fighting was reported in Croatia on Friday.

President Bush, ending his stay in Rome for the NATO conference, congratulated Europe for its leadership in attempts to settle the Yugoslav crisis but said the United States has not yet decided whether to join the economic boycott. Bush traveled to the Netherlands on Friday for talks with EC leaders on the Yugoslav crisis and other matters.

At the Vatican, a troubled Pope John Paul II underlined the "tragic urgency" of events in Croatia and the other Yugoslav republics in a one-on-one, 62-minute conversation with Bush. Vatican observers called the discussion remarkable for its frankness and cordiality.

Cyrus R. Vance, a former U.S. secretary of state and newly appointed U.N. trouble-shooter for Yugoslavia who was coincidentally in Rome on Friday, conferred at length with diplomats at the Vatican, where a privately circulated assessment details horrific loss of life and property.

By the Vatican's private count, 2,000 to 3,000 people, most of them civilians, are known to have died in heavily Roman Catholic Croatia, and the total deaths in ethnic strife could number 10,000. According to the report, there are up to 400,000 refugees in Croatia, where billions of dollars in property damage has occurred. To date, 22 convents and 241 churches have been destroyed or heavily damaged, including 11 Orthodox churches, two synagogues and seven Protestant churches, the Vatican report says.

Eleven European Community foreign ministers broke away from the larger NATO gathering Friday and were joined by their colleague from neutral Ireland, which is not a NATO member, to enact sanctions that they threatened to impose earlier this month if the latest cease-fire--No. 12--did not hold. And it did not.

The sanctions announced by Dutch Foreign Minister Hans van den Broek immediately suspend trade concessions, ban imports of Yugoslav textiles and strike Yugoslavia from a list of East European aid recipients. A loss of $900 million in promised EC economic assistance comes atop an earlier suspension of a $1-billion aid package. Canada quickly also announced export restrictions to Yugoslavia.

About 60% of Yugoslavia's trade is with EC members. Since pipelines from Croatian ports have been closed, it has received reduced supplies of oil by barge via the Danube from the Soviet Union and by truck from Greece. Hours-long lines for gas are facts of life in Belgrade and other Serbian cities.

Van den Broek said Europe's three current members on the U.N. Security Council--Britain, France and Belgium--will jointly ask the United Nations to improve enforcement of a longstanding but ineffective arms embargo and "to take the necessary steps toward imposing an oil embargo."

An EC statement warned Serbia, without naming it, that "the use of force and a policy of fait accompli to achieve changes of borders are illusory and will never be recognized by the Community and its member states."

Serbian irregulars, backed by the Serbian-dominated Yugoslav army, now control about one-third of Croatia, a republic of 4.7 million people with a Serbian minority of 12% or so.

The EC measures are directed against the hard-line Serbian government in Belgrade, capital of both Serbia and a moribund Yugoslavia. But they were announced against Yugoslavia because that is the only entity with which the Community has ties, EC Commissioner Abel Matutes noted.

Van den Broek said that "positive compensatory measures" would be applied to those of Yugoslavia's six republics that cooperate toward a peaceful solution. EC members whose commerce is adversely affected by the loss of Yugoslav trade also will be compensated; this particularly will affect Greece.

Diplomatic recognition of republics asserting their independence from a Serbian-dominated Yugoslavia can only come, Van den Broek said, "in the framework of an overall settlement that includes adequate guarantee for the protection of human rights and rights of national or ethnic groups."